This invention relates to a centralizer for use in deviated, highly deviated or horizontal well bores to center the casing in the well bore during cementing of the casing in the well bore. More specifically, the invention relates to a semi-rigid floating spring type centralizer for use in deviated, highly deviated or horizontal well bores to center the casing in the well bore during cementing of the casing in the well bore.
Typically prior art centralizers can be generally classified as fixed spring types, floating spring types, rigid types and combinations thereof. There are also various types of knock-down centralizers which may be fixed spring, floating spring, rigid or combination type centralizers.
In deviated, highly deviated or horizontal well bores it is desirable, in order to obtain better results in the cementing of the casing in the well bore, to have the casing in the or near the center of the well bore during cementing operations. If fixed spring and floating spring type centralizers are used, they will need to have high spring forces generated by the springs to ensure that the casing is centered in the well bore. However, these types of centralizers will need to be installed about the casing and held in position by either the casing collars or limit clamps installed on the casing. Since the casing collars and limit clamps will prevent the springs on the centralizers from fully deflecting during running of the casing in the well bore, high starting forces to start the centralizers into the well bore and high running forces to run and reciprocate the casing in the well bore will be present. If rigid type centralizers are used to center the casing in the well bore during cementing operations, the centralizer will be of smaller diameter than the well bore since it is rigid and contains no springs and will merely attempt to maintain a minimum distance between the casing and the well bore during cementing operations.
Combination types of rigid and floating spring type centralizers such as shown in U.S. Pat. Nos. 2,636,564 and 2,728,399 are an attempt to utilize the best features of both types of centralizers. However, since the springs are of a limited number the restoring force may not be sufficient to center the casing in the well bore or due to limited movement of the springs the starting and running forces generated by the centralizer may be high.